Stent delivery system

ABSTRACT

A stent delivery system to facilitate introduction and placement of a stent, including a catheter having an expandable distal portion constructed and arranged for expanding the outer diameter of the catheter from a contracted state to an expanded state: a stent positioned around the distal portion of the catheter having a contracted condition and being expandable to an expanded condition, and being sized in the contracted condition to closely surround the catheter in the contracted state, the expandable distal portion of the catheter including a balloon within which there is included on the catheter shaft at least one body of a diameter larger than the catheter shaft to which the stent and balloon are fitted, as by crimping, for holding the stent in place until it is released therefrom by expansion of the balloon and further including axially slidable sleeves over the stent in the unexpanded condition.

This application is a continuation of U.S. application Ser. No.09/387,179, filed Aug. 31, 1999, now U.S. Pat. No. 6,391,032, which is acontinuation of U.S. application Ser. No. 08/917,074, filed Aug. 22,1997, now U.S. Pat. No. 5,944,726, which is a Continuation-In-Partapplication based on U.S. Ser. No. 08/807,791 filed Feb. 28, 1997, nowU.S. Pat. No. 6,077,273, issued Jun. 20, 2000, entitled CATHETER SUPPORTFOR STENT DELIVERY which is a Continuation-In-Part based on U.S. Ser.No. 08/702,150 filed Aug. 23, 1996, now U.S. Pat. No. 6,007,543, issuedDec. 28, 1999, entitled STENT DELIVERY SYSTEM and U.S. Ser. No.08/697,453 filed Aug. 23, 1996, now abandoned, entitled PRE-MOUNTEDSTENT DELIVERY DEVICE WITH INFLATABLE TUBE COMPONENT, all of which areincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

In typical PTCA procedures, a guiding catheter is percutaneouslyintroduced into the cardiovascular system of a patient through a vesseland advanced through therein until the distal end thereof is at adesired location in the vasculature. A guidewire and a dilatationcatheter having a balloon on the distal end thereof are introducedthrough the guiding catheter with the guidewire sliding through thedilatation catheter. The guidewire is first advanced out of the guidingcatheter into the patient's coronary vasculature and the dilatationcatheter is advanced over the previously advanced guidewire until thedilatation balloon is properly positioned across the lesion. Once inposition across the lesion, the flexible, expandable, preformed balloonis inflated to a predetermined size with a liquid or gas at relativelyhigh pressures, such as greater than about four atmospheres, to radiallycompress the arthrosclerotic plaque of the lesion against the inside ofthe artery wall and thereby dilate the lumen of the artery. The balloonis then deflated to a small profile so that the dilatation catheter maybe withdrawn from the patients vasculature and blood flow resumedthrough the dilated artery.

In angioplasty procedures of the kind described above, there may berestenosis of the artery, which either necessitates another angioplastyprocedure, a surgical by-pass operation, or some method of repairing orstrengthening the area. To help prevent restenosis and strengthen thearea, a physician can implant an intravascular prosthesis formaintaining vascular patency, called a stent, inside the artery at thelesion. The stent is expanded to a larger diameter for placement in thevasculature, often by the balloon portion of the catheter. Stentsdelivered to a restricted coronary artery, expanded to a larger diameteras by a balloon catheter, and left in place in the artery at the site ofa dilated lesion are shown in U.S. Pat. No. 4,740,207 to Kreamer; U.S.Pat. No. 5,007,926 to Derbyshire; U.S. Pat. No. 4,733,665 to Palmaz;U.S. Pat. No. 5,026,377 to Burton et al.; U.S. Pat. No. 5,158,548 to Lauet al.; U.S. Pat. No. 5,242,399 to Lau et al.; U.S. Pat. No. 5,344,426to Lau et al.; U.S. Pat. No. 5,415,664 to Pinchuk; U.S. Pat. No.5,453,090 to Martinez et al.; U.S. Pat. No. 4,950,227 to Savin; U.S.Pat. No. 5,403,341 to Solar; U.S. Pat. No. 5,108,416 to Ryan et al. andEuropean Patent Application No. 707 837 A1 to Sheiban, all of which areincorporated herein by reference. A stent particularly preferred for usewith this invention is described in PCT Application No. 960 3092 A1,published Feb. 8, 1996, the content of which is also incorporated hereinby reference.

The present invention is particularly directed to improved arrangementsfor releasably attaching the stent to the catheter to facilitatedelivery thereof. Releasable sleeves are shown in U.S. Pat. No.4,950,227 to Savin. This patent is incorporated herein by reference.

SUMMARY OF THE INVENTION

This invention concerns apparatus suitable for delivery of stents tobody cavities. In general, stents are prosthetic devices which can bepositioned within a body cavity, for example, a blood vessel of the bodyof a living human or in some other difficultly accessible place. Thestent prosthesis is formed of a generally tubular body, the diameter ofwhich can be decreased or increased. Stents are particularly useful forpermanently widening a vessel which is either in a narrowed state, orinternally supporting a vessel damaged by an aneurysm. Such stents aretypically introduced into the body cavity by use of a catheter. Thecatheter is usually of the balloon catheter type in which the balloon isutilized to expand the stent, which is positioned over the balloon, toplace it in a selected location in the body cavity. The presentinvention is particularly directed to improved arrangements forreleasably attaching the stent to the catheter to facilitate deliverythereof. The stent is held in place on the catheter by means of anenlarged body carried by the catheter shaft within the balloon to whichthe stent and balloon are fitted, as by crimping in combination with oneor more sleeves releaseably overlying an end portion or portions of astent and balloon.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an isometric view, a portion of which is enlarged and inlongitudinal section, of a balloon catheter having a stent fixed to thecatheter over the balloon;

FIG. 2 is an even more enlarged view in longitudinal cross-section ofthe distal end portion of the catheter of FIG. 1;

FIG. 3 is a schematic showing of one form of retraction of thereleasable sleeve upon expansion of the balloon;

FIG. 4 is a schematic showing of another form of retraction of thereleasable sleeve upon expansion of the balloon;

FIG. 5 is yet another form of retraction of the releasable sleeve uponexpansion of the balloon;

FIG. 6 is a schematic showing of yet another form of retraction of thereleasable sleeve upon expansion of the balloon;

FIG. 7 is a schematic showing of a modified shape for the releasablesleeve;

FIG. 8 is a schematic showing in cross-section of another embodiment ofthe invention with a stent not yet mounted;

FIG. 9 is a schematic showing of another embodiment of the invention;and

FIG. 10 is a schematic showing of yet another embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2 a stent delivery system generally indicatedat 10 includes a balloon catheter 12 having a balloon 14 on a distal endportion generally indicated at 16. FIG. 1 shows a proximal portion ofthe catheter at 12 a and a distal portion 12 b in enlarged view. FIG. 2shows the distal end portion 16 in an even more enlarged view. Theillustrative catheter 12 is of the type known as an over the wirecatheter. However, other types of catheters may be used, such as rapidexchange/single operator and fixed wire types. The balloon 14 is fixedto the catheter 12 by standard means. The balloon is shown in itscontracted state in FIGS. 1 and 2. A stent 18 is fixed about the balloonby crimping it thereto. The stent has a larger expanded diameter whichis obtained when the balloon is expanded in the known manner. That is,the stent is released from the catheter upon expansion of the balloonwhen placed in a vessel. When the balloon is then deflated, removal ofthe balloon and catheter may be accomplished while leaving the stent inplace.

As is known in the art the balloon is either bonded at its ends byadhesive 20 and 22, respectively to the outer member 24 of the catheterand to the inner member 26 of the catheter in the manner as shown, or ismade one-piece with the outer member as is known in the art. Thecatheter balloon may be inflated by fluid (gas or liquid) from aninflation port extending from a lumen 28 contained in the catheter shaftand opening into the balloon as shown, or by other known arrangements,depending on the design of the catheter. The details and mechanics ofballoon inflation and specific overall catheter construction will varyaccording to the particular design involved in any given instance, andare known in the art per se. All variations are acceptable for use withthis invention.

Any balloon expandable stent may be used with this invention. Many areknown in the art including plastic and metal stents. Some are more wellknown such as the stainless steel stent shown in U.S. Pat. No.4,735,665; the wire stent shown in U.S. Pat. No. 4,950,227; anothermetal stent shown in European Patent Application No. EPO 707 837 A1 andthat shown in U.S. Pat. No. 5,445,646. All of these patents areincorporated herein by reference. Also, shape memory metal stents may beused. As already indicated the stent of PCT Application No. 960 3092 A1is particularly preferred.

The stent is typically about 16 mm long, while the balloon may be 20 mmlong. These dimensions, however, are merely representative forillustrative purposes only and are not meant to be limiting. The stentis positioned over the balloon portion of the dilatation catheter andgently crimped onto the balloon either by hand or with a tool such as apliers or the like to be mounted for delivery as shown in FIGS. 1 and 2.The crimping may be accomplished by either the manufacturer or thephysician.

In accordance with one embodiment of this invention, a mounting bodies30, seen in FIGS. 1 and 2 are included inside balloon 14 to provide acushion and/or substrate of enlarged diameter relative to the shaft tosupport and hold the stent and secure it during crimping and thedelivery procedure. The mounting bodies are preferably located in thebody portion of the balloon.

In the embodiment shown, mounting bodies 30 are ring-like in form andinner lumen 26, providing an enlarged area or portion for receiving theballoon and stent when the latter is crimped. Marker bands 32 and 34 mayalso be included on inner 26 as shown. Any radiopaque material such asgold is useful for this purpose. Although, the material of the mountingbodies may be hard, it is preferably of any thermoplastic elastomerhaving elastic or deformable properties, more preferably of a relativelyresilient elastomer material, e.g., silicone, preferably a lowerdurometer silicone or polyurethane, such as Tecothane 1055D. Adeformable thermoplastic material such as high density polyethylene(HDPE) may be used. Any deformation of resilient material of themounting body when the stent/balloon is crimped to it causes a radialoutward force on the stent/balloon increasing the friction therebetweendespite a recoil of the stent.

The stent is also fixed in position by two overlying retaining sleeves36 and 38. Sleeves 36 and 38 are formed of polyurethane, preferablyTecothane 1055D, and are axially fixed on catheter 12 by adhesive plugs40 and 42 of urethane adhesive. The plugs of adhesive may be tapered tothe catheter as shown to facilitate movement of the catheter in avessel. The sleeves overlap the marginal end portions of stent 18 asshown.

A lubricating solution such as silicone fluid may be used betweenballoon 14 and sleeves 36 and 38 and thereon to facilitate release ofstent 18 from the sleeves.

During delivery, the balloon catheter is advanced through and positionedin a patient's vasculature so that the stent is adjacent to the portionof the vessel where treatment is to take place. The balloon is inflatedto expand the stent to an enlarged diameter. At this time, expansion ofthe balloon causes the end margin of the sleeves to slide axially fromover the stent thereby releasing the ends of the stent from thecatheter. Various forms of retraction of sleeves 36 and 38 are shown inFIGS. 3-6. These figures illustrate the configuration of the sleeves 36and 38 in their retracted state after the balloon 14 has been fullyexpanded. Only the distal sleeve 38 is shown. FIG. 3 illustrates thepreferably retraction configuration. To promote easier retractionsleeves are coated with silicone. The sleeves are preferably adhered tothe outer shaft 24 and the inner shaft 26 at point 40 (not shown), 42,but may be adhered further up the waste 41 of the balloon. Theretraction configurations may be controlled by either pre-creasing thesleeves or adhering the sleeve to a point further up on the waist of theballoon. The sleeves have a tendency of folding at a pre-fold crease orat the point of adherence. A preferred cone angle of 45° for the balloonis shown in FIG. 6, which shows an expanded balloon 14 and retractedsleeves 36,38. When the stent has reached the desired diameter, theballoon is deflated so that the catheter may be removed leaving thestent in place.

A modified sleeve 39 configuration is shown in FIG. 7 in stepped form 43having a large diameter at 44 in one section 46 and a small diameter 45in a second section 50.

FIGS. 8-10 show alternative embodiments of the invention. Specifically,alternative positioning and number of mounting bodies 30. These figuresshow an unexpanded balloon having the mounted bodies 30 within theballoon. They are meant to illustrate essentially the same structure asshown in FIG. 2 differing only in the number and positioning of themounted bodies 30. In the embodiment shown in FIG. 8, the ring-likemounting body 30 is singular. Another similar version is shown in FIG. 9which includes three ring-like mounting bodies 30. The embodiment shownin FIG. 10 includes four ring-like mounting bodies 30.

The above Examples and disclosure are intended to be illustrative andnot exhaustive. These examples and description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

What is claimed is as follows:
 1. A stent delivery system comprising incombination: a catheter having a distal region and an inner shaft; anexpandable balloon mounted on and about the catheter at the distalregion, said expandable balloon having an expanded state, a collapsedstate, a first waist, a second waist, a first cone portion, a secondcone portion and a body portion, wherein the cone portions are betweenthe body portion and the waists, respectively and wherein the firstwaist and the second waist are secured to the catheter; an expandablestent mounted on and about the expandable balloon, the expandable stenthaving a first end, a second end, a collapsed state and an expandedstate; at least one stent retaining sleeve, said at least one stentretaining sleeve having a length and a resting diameter, wherein theresting diameter is substantially constant along its length, a first endportion and a second end portion, wherein the second end portion coversthe first end of the expandable stent, the at least one stent retainingsleeve having a region which is pre-creased, such that, when theexpandable balloon expands, the at least one stent retaining sleevefolds onto itself at the region which is pre-creased.
 2. The stentdelivery system of claim 1, wherein the at least one stent retainingsleeve folds inwardly relative to the catheter distal region when theexpandable balloon is expanded.
 3. The stent delivery system of claim 1,wherein the at least one stent retaining sleeve folds outwardly relativeto the catheter distal region when the expandable balloon is expanded.4. The stent delivery system of claim 1, wherein the at least one stentretaining sleeve has at least two pre-creases, wherein the at least onestent retaining sleeve folds at the at least two pre-creases when theexpandable balloon is expanded.
 5. The stent delivery system of claim 1,wherein the at least one stent retaining sleeve has three pre-creases,wherein the at least one stent retaining sleeve has three folds when theexpandable balloon is expanded.
 6. The stent delivery system of claim 1,wherein the pre-crease is circumferential.
 7. A stent delivery systemcomprising in combination: a catheter having a distal region and aninner shaft; an expandable balloon mounted on and about the catheter atthe distal region, said expandable balloon having an expanded state, acollapsed state, a first waist, a second waist, a first cone portion, asecond cone portion and a body portion, wherein the cone portions arebetween the body portion and the waists, respectively and wherein thefirst waist and the second waist are secured to the catheter; anexpandable stent mounted on and about the expandable balloon, theexpandable stent having a first end, a second end, a collapsed state andan expanded state; at least one stent retaining sleeve, said at leastone stent retaining sleeve having a length, a first end portion and asecond end portion, wherein the second end portion covers the first endof the expandable stent, the at least one stent retaining sleeve havinga first portion having a first resting diameter, a second portion havinga second resting diameter and a step formed between the first portionand the second portion, wherein the second resting diameter is greaterthan the first resting diameter and wherein the second end portion ofthe at least one stent retaining sleeve is part of the second portion ofthe at least one stent retaining sleeve and wherein, when the expandableballoon is in its collapsed state, the at least one stent retainingsleeve is in contact with the expandable balloon along the sleeve'slength where the at least one stent retaining sleeve is radiallyadjacent to the expandable balloon.
 8. The stent delivery system ofclaim 7, wherein the step is positioned directly adjacent to and hugsthe first end of the expandable stent.
 9. The stent delivery system ofclaim 7, wherein the first portion of the at least one stent retainingsleeve is bonded to at least a portion of the first waist of theexpandable balloon.
 10. The stent delivery system of claim 9, the firstportion of the at least one stent retaining sleeve having an axiallength, wherein the first portion of the at least one stent retainingsleeve is bonded to the first waist of the expandable balloonsubstantially along the axial length of the first portion of the atleast one stent retaining sleeve.
 11. The stent delivery system of claim1, wherein, when the at least one stent retaining sleeve folds ontoitself at the region which is pre-creased, it forms an acute angleextending from the pre-creased region.